In removing oxide scale formed on the surface of a strip steel plate, common practice is to guide this strip steel plate into an acid pickling tank filled with an acid liquid by a guide roll, and cause the strip steel plate to travel in the acid liquid, thereby washing and removing the oxide scale on the surface by means of the acid liquid. For this purpose, an acid pickling device is available which comprises two or more acid pickling tanks connected together, the acid pickling tanks being filled with an acid liquid of different acid concentrations, and in which a strip steel plate is caused to travel in the acid pickling tanks sequentially to remove oxide scale on the surface of the strip steel plate reliably.
FIG. 8 is a schematic side view of a conventional acid pickling device.
In the conventional acid pickling device, as shown in FIG. 8, an acid pickling tank body 101 is partitioned with a partition wall 102 into a first tank 103 and a second tank 104, and the first tank 103 and the second tank 104 are almost the same in constitution. That is, the first tank 103 and the second tank 104 are open upwards, and they are filled with acid liquids L.sub.1 and L.sub.2, respectively, of different concentrations for acid pickling of a strip steel plate S. A lid 105 is attached to the top of the acid pickling tank body 101 to form an inlet portion 106 in the first tank 103, and an outlet portion 107 in the second tank 104. To the inlet portion 106, an aerial deflector roll 108 and an immersion deflector roll 109 are attached. To the outlet portion 107, an aerial deflector roll 110 and an immersion deflector roll 111 are attached. To an intermediate portion, an aerial deflector roll 112 and immersion deflector rolls 113 are attached.
From a lower surface of the lid 105, ceiling plates 115, 116 are suspended via engagingly stopping portions 114 for immersion in the first tank 103 and the second tank 104, respectively. From the ceiling plates 115, 116, bottom plates 117, 118 are suspended via connecting plates (not shown) located at both side parts. On the lower surface of the ceiling plates 115, 116, many immersion guide rolls 119, 120 rotatable via bearing portions are mounted along a direction of travel of the strip steel plate S. On the upper surface of the bottom plates 117, 118, many skids 121, 122 are attached at positions opposed to the immersion guide rolls 119, 120.
Thus, the strip steel plate S is guided by the aerial deflector roll 108 and the immersion deflector roll 109 at the inlet portion 106 into the acid liquid L.sub.1 of the first tank 103, and travels, while being guided, between the immersion guide rolls 119 and the skids 121. At this time, oxide scale formed on the surface of the strip steel plate S is washed with the acid liquid L.sub.1 and removed thereby. Then, the strip steel plate S is guided by the aerial deflector roll 112 and the immersion deflector roll 113 to pass over the partition wall 102 and come into the acid liquid L.sub.2 of the second tank 104. Then, the strip steel plate S travels, while being guided, between the immersion guide rolls 120 and the skids 122. On this occasion, the oxide scale formed on the surface of the strip steel plate S is washed with the acid liquid L.sub.2 and removed thereby. Then, the strip steel plate S is guided by the immersion deflector roll 111 and the aerial deflector roll 110 at the outlet portion 107, and delivered outside of the second tank 104.
Such a conventional acid pickling device is disclosed, for example, in Japanese Unexamined Patent Publication No. 5-78870.
With the foregoing conventional acid pickling device, the acid pickling tank body 101 is divided into the first tank 103 and the second tank 104 by the partition wall 102 so that the acid liquids L.sub.1 and L.sub.2 do not mix. Because of this configuration, when the strip steel plate S moves from the first tank 103 to the second tank 104, the strip steel plate S is guided, in a bent shape, by the aerial deflector roll 112 and the immersion deflector rolls 113. This plate S is once pushed out of the first tank 103, and then entered into the second tank 104. At this time, a great bending stress acts on the strip steel plate S, increasing the tension of the strip steel plate S in the entire acid pickling device, and consuming a high operating power.
Furthermore, when the strip steel plate S moves from the first tank 103 to the second tank 104, it is guided by the aerial deflector roll 112 and the immersion deflector rolls 113. Thus, these rolls 112, 113 inevitably contact the acid liquid L.sub.1. This requires their constant mounting and dismounting for maintenance, increasing the running cost.
The present invention has been accomplished in an attempt to solve the above problems. Its object is to provide an acid pickling device of a decreased cost, and with an increased efficiency of acid pickling treatment for a strip plate.